The invention relates to a clamp device for the cylinder wiper blade, or `doctor`, of a rotogravure printing machine.
In rotary machines of the type in question, use is made of engraved cylinders that are inked by methods known to those skilled in the art.
Use is also made of blades, one pressed against each cylinder, for the purpose of wiping and removing surplus ink from non-engraved parts of the surface. The blade is breasted flat against a back-up iron and carried by a bar, to which both are clamped by tightening a set of screws spaced apart at regular intervals along the entire length of the bar.
This system of clamping the bar presents a number of different drawbacks.
A first drawback is attributable to the fact that the clamp screws are tightened by hand; a uniform distribution of clamping pressure cannot therefore be obtained along the length of the blade, and the blade thus undulates, being notably thin and readily deformable.
Undulation of the blade is always encountered with conventional clamping systems, and dictates the need to exert a considerable amount of pressure on the blade in order to ensure a faultless wiping action. This intense mechanical pressure gives rise to early wear on the cylinder, and consequently, to increased running costs.
A further drawback is created by the fact that some considerable time is needed to replace the blade. Yet another drawback stems from the fact that the blade must be sharpened more often, the greater the pressure on the cylinder.
Accordingly, the object of the invention is one of overcoming the drawbacks mentioned above, and more particularly, of reducing the pressure with which the blade is offered to the cylinder.
In order to reduce this pressure, one must solve the problem of how a constant clamping action may be applied to blade and bar along the entire length of the blade, so as to ensure perfect straightness from end to end.